Chickpea flour is a ground flour made from chickpeas. In Italy it is called farina di ceci and is used to make socca and cecina.
Note that Indian gram flour (besan), while it is made with a type of chickpea, is not usually a substitute for Western chickpea flour. Most gram flour is made with brown chickpeas (Bengal Gram) or black chickpeas; American chickpea flour is typically made with white chickpeas.